In U.S. Pat. No. 3,067,279, issued Dec. 4, 1962, to Benjamin P. Baker, there is illustrated and described a vapor-cooled bushing. The vapor utilized in the Baker bushing boiled and ascended as a vapor to a heat-exchanger disposed at the upper end of the Baker terminal-bushing, which was located externally of the oil-tank casing, which enclosed the interrupting structure. Heat, generated at the stationary contact, secured to the lower end of the Baker-cooled bushing, was transmitted to the vapor to be dissipated externally of the oil-tank structure, as well as the I.sup.2 R losses generated within the terminal-lead itself. Also, Lapp-U.S. Pat. No. 2,953,629 issued 9/20/60 is of interest, as is Moore--U.S. Pat. No. 3,627,899, issued Dec. 14, 1971.